Liquibase：在DB2中将列更改为自动递增列（标识）

Question

I'm trying to change a BIGINT Column to an autoincremented column in DB2 but I can't seem find how. I tried doing it like this:

    <changeSet id="08.01" author="...">
        <addColumn tableName="table_name">
            <column name="id" type="bigint">
                <constraints nullable="true"/>
            </column>

            <column name="member_type" type="varchar(100)">
                <constraints nullable="true"/>
            </column>
        </addColumn>
    </changeSet>

    <changeSet id="08.02" author="...">
        <addAutoIncrement tableName="table_name"
                          columnDataType="bigint"
                          columnName="id"/>
    </changeSet>

and when it runs I get this error:

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'liquibase' defined in class path resource [org/springframework/boot/autoconfigure/liquibase/LiquibaseAutoConfiguration$LiquibaseConfiguration.class]: Invocation of init method failed; nested exception is liquibase.exception.MigrationFailedException: Migration failed for change set classpath:db/changelog/08-separation.xml::08.01::author:
     Reason: liquibase.exception.DatabaseException: DB2 SQL Error: SQLCODE=-270, SQLSTATE=42997, SQLERRMC=72, DRIVER=4.13.127 [Failed SQL: ALTER TABLE SCHEMATEST.table_name ALTER COLUMN id SET GENERATED BY DEFAULT AS IDENTITY]
    at org.springframework.bean
...
...
...
Caused by: liquibase.exception.MigrationFailedException: Migration failed for change set classpath:db/changelog/08separation.xml::08.01::author:
     Reason: liquibase.exception.DatabaseException: DB2 SQL Error: SQLCODE=-270, SQLSTATE=42997, SQLERRMC=72, DRIVER=4.13.127 [Failed SQL: ALTER TABLE SCHEMATEST.table_name ALTER COLUMN id SET GENERATED BY DEFAULT AS IDENTITY]
...
...
...
Caused by: com.ibm.db2.jcc.am.SqlSyntaxErrorException: DB2 SQL Error: SQLCODE=-270, SQLSTATE=42997, SQLERRMC=72, DRIVER=4.13.127

Answer 1

An identity column cannot be nullable, this is what the error message tells you :

A nullable column cannot be changed to become an identity column.

Change the column constraint to nullable="false" I guess.

Answer 2

I found an answer myself at this link and the explanation is this:

Every DB2 admin discovers sooner or later that DB2 can not add identity column to existing table easily. Following statements fails due to syntax error: alter table public.clicks add column id integer generated always as identity But i have good news for everyone. It can be still done, but it requires more steps.

1. Add not null integer column You need to provide default value for it otherwise db2 will refuse it to make not null alter table public.clicks add column id integer not null default 0

2. Drop default value from column I am not exactly sure why it is needed because some manuals on internet omits this step but i was not able to make it work without this on DB2 9.7.3 LUW alter table public.clicks alter column id drop default

3. Now set column to always generated ( add the autoincrement ) alter table public.clicks alter column id set generated always as identity

4. Reorg table to make it writeable (I didn't do this and it still works) reorg table public.clicks

5. Now replace zeros with generated itentity values update public.clicks set id = default

6. And optionally make id column primary key for table alter table public.clicks add constraint pkey primary key(id)

And the liquibase code for it:

defaultSchemaNames comes from spring properties which I defined like this. I don't know if there's a better way to get the schema but this one works also

# in application.properties I've set this
liquibase.parameters.defaultSchemaName=MY_SCHEMA_NAME

The liquibase.xml

    <property name="defaultSchema" value="${defaultSchemaName}" /> 

    <changeSet id="08.01.00" author="alex@mail.com">
        <dropPrimaryKey tableName="members" constraintName="pk_members_relation"/>
    </changeSet>

    <changeSet id="08.01" author="alex@mail.com">
        <addColumn tableName="members">
            <column name="id" type="BIGINT" defaultValue="0">
                <constraints nullable="false"/>
            </column>

            <column name="member_type" type="varchar(100)">
                <constraints nullable="true"/>
            </column>
        </addColumn>
    </changeSet>

    <changeSet id="08.02" author="alex@mail.com">
        <dropDefaultValue tableName="members" columnName="id"/>
    </changeSet>

    <changeSet id="08.03" author="alex@mail.com">
        <addAutoIncrement tableName="members" columnName="id" columnDataType="bigint"/>
    </changeSet>

    <changeSet id="08.04" author="alex@mail.com">
        <sql>
            UPDATE ${defaultSchema}.members SET id = default
        </sql>
    </changeSet>